Israeli scientists say they have studied a type of coral whose bleaching is triggered by a bacterium, and found that this is carried and transmitted by a coral-feeding worm. If the same is true for other corals, scientists may be able to prevent the disease by targeting the worm vector, just as they control malaria by targeting mosquitoes.
Corals depend on algae inside their bodies to provide carbohydrates and oxygen through photosynthesis. This partnership allows corals to thrive in infertile areas of ocean, and explains why reef communities are so rich. But when water temperature rises, the algae either die or the corals eject them in response to the stress of the heat. Before too long the entire reef turns white. It is unclear how well reefs later recover, and the sharp rise in coral bleaching since the 1980s has sparked dire predictions for their future (see Box).
Most marine biologists agree that bleaching is caused by rising sea temperatures, and the best way to stop it is to cut carbon emissions. But that is an indirect, long-term strategy that may not save reefs in time. Now there may be a more immediate remedy.
In the late 1990s, Yossi Loya and Eugene Rosenberg led a team from Tel Aviv University that found a bacterium that causes coral bleaching. Crucially, it turns out to be more virulent at higher temperatures. "Coral biologists are not microbiologists," says Rosenberg. "They saw the association of bleaching with temperature, but they did not see the bacterium."
The microbe, named Vibrio shiloi, was responsible for bleaching the stony coral Oculina patagonica in the Mediterranean Sea. But researchers were mystified because th
Contact: Claire Bowles